The reference to any prior art in this specification is not, and should not be taken as an acknowledgement or any form of suggestion that the prior art forms part of the common general knowledge.
The spine is a complex, flexible structure which can change its shape and move in all directions. It consists of vertebrae, intervertebral discs, and intervertebral joints (which are attached to ribs in the thoracic area) which house the spinal cord and the nerves leading out to the body. Protection of this complex and vulnerable structure during sustained or heavy loading which involves the spine can only be achieved by appropriate muscle function which serves to hold the spine in its ‘neutral’ position.
The neutral spine, which is formed by three spinal curves (cervical, thoracic and lumbo-sacral curves), is usually described as the ‘S’ shape, neutral spine position. The curves are formed by the shape of the vertebrae and the intervertebral discs, and, most importantly, by muscles which hold the shape of the three curves. The three curves allow the spine to act as a spring to withstand stress and negate impact loads caused by the vertical force of gravity. The individual curves making up the neutral spine position lie each side of the vertical line of good posture, that is, the imaginary line, viewed from the side, through the mastoid process, centre of the shoulder joint and the centre of the hip joint. Descriptions of the individual curves are as follows:                (i) curve of the neck region—the concave cervical spinal curve lies in front of the vertical line and is closely linked to the position of the head;        (ii) curve of the low back—the concave lumbo-sacral spinal curve also lies in front of the vertical line, and is closely linked to movement of the pelvis and lower limb; and        (iii) curve of the thorax (ribs attached)—in contrast to the neck and low back regions, the convex thoracic curve lies behind the vertical line of good posture.        
The convex thoracic curve is closely linked to movement and position of the scapula and associated upper limb. To hold the thoracic curve firm, the scapulo-thoracic muscles (mainly serratus anterior) must produce a backwardly directed muscle force on the spine whilst also causing the scapula to become flat against the chest wall. This action can only be produced with concomitant activation and strengthening of the scapulo-thoracic muscles (mainly serratus anterior) through weight-bearing exercise for the upper limb [see the ‘weightbearing’ test for serratus anterior described in Kendall et al. ‘Muscles: Testing and Function, with. Posture and Pain’, Lippincott Williams & Wilkins, 2005]. In a healthy spine with scapulo-thoracic muscles (mainly serratus anterior) working correctly, the thoracic spine retains its curve, and the scapula is held flat against the rib cage.
The complex structure of the spine is protected and managed through a specialised deep muscle system which supports and holds the three individual curves of the neutral spine. Serratus anterior muscle forms an important part of this deep muscle system. Maintenance of the neutral spine position is important when the spine is dealing with sustained or heavy loading and importantly, to provide a firm central axis for axial rotation (twisting) activities of the spine. Activities where maintenance of a neutral spine is important include the following:                (i) walking (low loading for the spine), where the neutral spine is held firm and supported for sustained periods in a upright position and gives the classic ‘good postural form’;        (ii) prolonged leaning forward activities requiring increased sustained loading (as required by certain occupations, for example, dentist or factory worker) where the spine requires strong muscles to support it in the neutral spine position;        (iii) sports such as golf, cricket and tennis which involve trunk twisting, where the spine requires short periods of using even stronger spinal muscles to allow the neutral spine position to form a strong central axis for trunk rotation (in the lean forward position); and        (iv) lifting, as safe lifting techniques depend on maintaining a strong neutral spine position. In particular, when lifting very heavy loads, the spine requires even stronger spinal muscles to maintain the neutral spine position in a lean forward position which is often accompanied by twisting movements.        
As a result of more sedentary modern lifestyles and robotic technology, people are developing poor spinal postures. In other words, people's spines are weakening and they are losing the ability to hold the upright neutral spine position. Weakness of the muscles controlling the spinal curves is also a result of lack of weight-bearing exercise for the upper limbs. Consequently, spinal structures are becoming far more vulnerable to injury, increasing spinal pain, disc injury and referred pain, osteoarthritis and other painful joint problems of the shoulder and hip.
General weakness of the spine is demonstrated with a loss of the normal, natural spinal curves each side of the vertical line of good posture. Loss of the natural spinal curves can take many forms, but during exercise it mostly results in the spine having a ‘C’ shaped curve or a reversed ‘C’ shape. Exercise with the spine in either of these positions will weaken, rather than strengthen, the spine.
Thus the neutral spine position is considered important for our musculo-skeletal health as, in this position, the muscles are capable of supporting and protecting the spine from injury. It is particularly the activation and strengthening of muscles that maintain the thoracic curve that has not been addressed in exercises currently used to strengthen the neutral spine.
Specifically for the thoracic curve, weakness of the serratus anterior muscle when standing upright is demonstrated by a flattened thoracic curve and ‘winging’ of the scapula, where the medial border of the scapula lifts away from the chest wall and protrudes far more posteriorly than the thoracic spine (see FIG. 4).
The serratus anterior muscle lies very deep under the large bone of the scapula, so facilitation techniques normally used to activate and train superficial muscles cannot be used. In addition, because the serratus anterior lies under bone, it cannot be viewed, facilitated or strengthened using real-time ultrasound imaging techniques (which are used as feedback techniques).
To ensure the stability and strength of the scapula-thoracic region, a specific type of strengthening exercise is required. This consists of an upper limb weight-bearing exercise, with axial (weight-bearing) resistance providing axial-compression longitudinally through the whole upper limb, as well as producing a backwardly directed muscle force to strengthen the curve of the thoracic spine. It is important when performing upper limb weight-bearing exercise that correct postural form is maintained in order to maintain the correct position of the thoracic curve.
There thus exists a need for a new feedback exercise device, to assist in strengthening weak muscles of the scapula-thoracic region as well as help monitor and maintain good posture. Such a device necessarily needs to specifically strengthen the serratus anterior in its weight-bearing role of displacing the thorax posteriorly and holding the scapula flat against the chest wall. This type of exercise would strengthen the thoracic curve and in turn strengthen the whole neutral spine position.
International Patent Publication, WO 2007/134380, describes a feedback device used to monitor the position of the lumbo-sacral curve and ensure the correct muscles are working. Feedback exercise tools are particularly important as they give feedback to a person as to whether or not the three spinal curves are being maintained and therefore whether or not the deep muscles supporting them are being exercised.
It would be desirable to have a feedback exercise device that allows the user to feel the position of the thoracic spine and the position of the scapula in relation to the thoracic spine. The user of such an exercise device could therefore undertake upper limb weight-bearing exercise to strengthen the scapulo-thoracic muscles (mainly serratus anterior) whilst maintaining correct postural form and thus properly maintaining the curve of the thoracic spine. Such an exercise device could also be used to maintain correct postural form and thus the correct position of the thoracic curve, during daily activities or when sitting for prolonged periods.
Despite a need for a feedback exercise device that allows the user to feel the position of the thoracic spine and the position of the scapula in relation to the thoracic spine and thus provides feedback as to correct postural form and maintenance of the thoracic curve, such a device has not been provided.